Population dynamics and life history traits of the non-indigenous Paranthura japonica Richardson (1909) in a recently invaded Mediterranean site

Abstract

Most of marine non-indigenous species still suffers of large gaps in knowledge even regarding the most basic life history traits. The present study aims to understand the biology and ecology of the pacific isopod Paranthura japonica in a newly invaded site in the Central Mediterranean Sea, specifically focusing on its population dynamics in response to seasonal variation of environmental parameters. To collect standardised samples of this minute benthic species with cryptic behaviour, we use nylon bath sponges as Artificial Substrate Units, and an image analysis software for digital measurements of total body length. We conclude that P. japonica, native to the cold Okhotsk sea, has well adapted to the warmer Mediterranean conditions. Its population has been found well-established and persistent throughout the year, while its numeric positive response to increasing temperature was one of our most surprising findings. In fact, reproductive events occur throughout the year, but peak during summer months. Finally, we show that nylon bath sponges represent an efficient artificial substrate for obtaining quantitative samples of peracarid crustaceans.